JP3674827B2 - Reversible thermosensitive recording material - Google Patents

Description

（式１中、ｑは１以上３以下の整数を表す。Ｒ ³ は炭素数１から１１の二価の脂肪族炭化水素基を表す。Ｒ ⁴ は鎖中に酸素原子あるいは硫黄原子を含んでも良い炭素数６から１１の脂肪族炭化水素基を表す。Ｚはジアシルヒドラジド（−ＣＯＮＨＮＨＣＯ−）、シュウ酸ジアミド（−ＮＨＣＯＣＯＮＨ−）、アシル尿素（−ＣＯＮＨＣＯＮＨ−、−ＮＨＣＯＮＨＣＯ−）、３−アシルカルバジン酸エステル（−ＣＯＮＨＮＨＣＯＯ−）、セミカルバジド（−ＮＨＣＯＮＨＮＨ−、−ＮＨＮＨＣＯＮＨ−）、アシルセミカルバジド（−ＣＯＮＨＮＨＣＯＮＨ−、−ＮＨＣＯＮＨＮＨＣＯ−）、ジアシルアミノメタン（−ＣＯＮＨＣＨ ₂ ＮＨＣＯ−）、１−アシルアミノ−１−ウレイドメタン（−ＣＯＮＨＣＨ ₂ ＮＨＣＯＮＨ−、−ＮＨＣＯＮＨＣＨ ₂ ＮＨＣＯ−）、マロンアミド（−ＮＨＣＯＣＨ ₂ ＣＯＮＨ−）から選ばれる二価の連結基の何れかを表す。）
【００１２】
【化５】

（式２中、ｒは１以上３以下の整数を表す。Ｒ⁵は炭素数２から１１の二価の炭化水素基を、Ｒ⁶は鎖中に酸素原子あるいは硫黄原子を含んでいてもよい炭素数１から２４の炭化水素基を表す。ＱおよびＴは同義であり、互いに同じであっても、異なっていてもよいアミド（−ＣＯＮＨ−、−ＮＨＣＯ−）、尿素（−ＮＨＣＯＮＨ−）、ウレタン（−ＮＨＣＯＯ−、−ＯＣＯＮＨ−）、ジアシルヒドラジド（−ＣＯＮＨＮＨＣＯ−）、シュウ酸ジアミド（−ＮＨＣＯＣＯＮＨ−）、アシル尿素（−ＣＯＮＨＣＯＮＨ−、−ＮＨＣＯＮＨＣＯ−）、３−アシルカルバジン酸エステル（−ＣＯＮＨＮＨＣＯＯ−）、セミカルバジド（−ＮＨＣＯＮＨＮＨ−、−ＮＨＮＨＣＯＮＨ−）、アシルセミカルバジド（−ＣＯＮＨＮＨＣＯＮＨ−、−ＮＨＣＯＮＨＮＨＣＯ−）、ジアシルアミノメタン（−ＣＯＮＨＣＨ ₂ ＮＨＣＯ−）、１−アシルアミノ−１−ウレイドメタン（−ＣＯＮＨＣＨ ₂ ＮＨＣＯＮＨ−、−ＮＨＣＯＮＨＣＨ ₂ ＮＨＣＯ−）、マロンアミド（−ＮＨＣＯＣＨ ₂ ＣＯＮＨ−）から選ばれる二価の基の何れかを表す。）
【００１３】
【化６】

（式３中、Ｒ⁷、Ｒ⁸、およびＲ⁹は同義であり、互いに同じであっても、異なっていてもよいアルキル基、アラルキル基、アルケニル基およびアリール基を表し、更にこれらは置換基を持っていても、互いに環を形成していてもよい。Ｒ¹⁰は炭素数６から２４の炭化水素基を表す。ｔは１または２を表す。Ａはアニオンを表し、ｗは分子内の電荷を０に調整するのに必要な数を表す。）
【００１４】
本発明に用いられる、一般式（１）〜（２）で表される可逆性顕色剤は、先に本出願人が見い出した特開平７−１０８７６１号公報、同７−１７９０４３号公報、同７−１６４７４６号公報、特願平１１−６９７８７号明細書、特願平１０−３１５２５２号明細書等の化合物であり、合成方法についても記載している。
【００１５】
一般式（１）で表される化合物中、Ｒ ³ は炭素数１から１１の二価の脂肪族炭化水素基を表す。Ｒ ⁴ は鎖中に酸素原子あるいは硫黄原子を含んでも良い炭素数６から１１の脂肪族炭化水素基を表す。Ｚはジアシルヒドラジド（−ＣＯＮＨＮＨＣＯ−）、シュウ酸ジアミド（−ＮＨＣＯＣＯＮＨ−）、アシル尿素（−ＣＯＮＨＣＯＮＨ−、−ＮＨＣＯＮＨＣＯ−）、３−アシルカルバジン酸エステル（−ＣＯＮＨＮＨＣＯＯ−）、セミカルバジド（−ＮＨＣＯＮＨＮＨ−、−ＮＨＮＨＣＯＮＨ−）、アシルセミカルバジド（−ＣＯＮＨＮＨＣＯＮＨ−、−ＮＨＣＯＮＨＮＨＣＯ−）、ジアシルアミノメタン（−ＣＯＮＨＣＨ ₂ ＮＨＣＯ−）、１−アシルアミノ−１−ウレイドメタン（−ＣＯＮＨＣＨ ₂ ＮＨＣＯＮＨ−、−ＮＨＣＯＮＨＣＨ ₂ ＮＨＣＯ−）、マロンアミド（−ＮＨＣＯＣＨ ₂ ＣＯＮＨ−）から選ばれる二価の連結基の何れかを表す。）一般式（１）において、ベンゼン環とＲ ³ との連結基は酸素原子であるが、一般的に消去性が良好であることから、Ｒ ³ 、Ｒ ⁴ の炭化水素基は短めに、更にＸで表されるアミド結合を最小構成単位とする連結基は水素結合能力が小さめの方が発色性を補え、発消色バランスの良好なものとなる傾向にある。
【００１６】
以下に、一般式（１）で示される電子受容性化合物の具体例を化７に挙げるが、本発明はこれに限定されるものではない。
【００１７】
【化７】

【００１８】
一般式（２）で表される化合物中、Ｒ ⁵ は炭素数２から１１の二価の炭化水素基を、Ｒ ⁶ は鎖中に酸素原子あるいは硫黄原子を含んでいてもよい炭素数１から２４の炭化水素基を表す。ＱおよびＴは同義であり、互いに同じであっても、異なっていてもよいアミド（−ＣＯＮＨ−、−ＮＨＣＯ−）、尿素（−ＮＨＣＯＮＨ−）、ウレタン（−ＮＨＣＯＯ−、−ＯＣＯＮＨ−）、ジアシルヒドラジド（−ＣＯＮＨＮＨＣＯ−）、シュウ酸ジアミド（−ＮＨＣＯＣＯＮＨ−）、アシル尿素（−ＣＯＮＨＣＯＮＨ−、−ＮＨＣＯＮＨＣＯ−）、３−アシルカルバジン酸エステル（−ＣＯＮＨＮＨＣＯＯ−）、セミカルバジド（−ＮＨＣＯＮＨＮＨ−、−ＮＨＮＨＣＯＮＨ−）、アシルセミカルバジド（−ＣＯＮＨＮＨＣＯＮＨ−、−ＮＨＣＯＮＨＮＨＣＯ−）、ジアシルアミノメタン（−ＣＯＮＨＣＨ ₂ ＮＨ ＣＯ−）、１−アシルアミノ−１−ウレイドメタン（−ＣＯＮＨＣＨ ₂ ＮＨＣＯＮＨ−、−ＮＨＣＯＮＨＣＨ ₂ ＮＨＣＯ−）、マロンアミド（−ＮＨＣＯＣＨ ₂ ＣＯＮＨ−）から選ばれる二価の基の何れかを表す。
【００１９】
以下に、一般式（２）で示される電子受容性化合物の具体例を化８に挙げるが、本発明はこれに限定されるものではない。
【００２０】
【化８】

【００２１】
一般式（３）で表される化合物中、Ｒ⁷、Ｒ⁸およびＲ⁹は同じであっても、異なっていてもよいアルキル基、アラルキル基、アルケニル基およびアリール基を表すが、好ましくは炭素数が６以下の低級アルキル基である。更にこれらは互いに連結して脂環構造を形成してもよいが、この時、酸素原子あるいは窒素原子等のヘテロ原子を鎖中に含有していてもよい。また、Ｒ¹⁰は炭素数６〜２４の一価もしくは二価の炭化水素基を表すが、好ましくは脂肪族炭化水素基であり、具体的には炭素数８から１８の一価である。Ａはカウンターアニオンを表すが、これらの具体例としては、ハロゲン、置換スルホネート、置換ボレート、置換ホスフェート等が挙げられ、好ましくは、ハロゲン、置換スルホネートである。
【００２２】
一般式（３）で表される化合物の具体例としては以下の化９および化１０に示す化合物が挙げられるが本発明はこれに限定されない。
【００２３】
【化９】

【００２４】
【化１０】

【００２５】
一般式（３）で表される化合物の好ましい使用量は、一般式（１）〜（２）で表される電子受容性化合物に対し０．１重量％以上１０００重量％以下であり、より好ましくは０．５重量％以上２００重量％以下である。更に、印字画像の耐熱保存性を考慮すれば、１重量％以上１００重量％以下が最も好ましい。また、一般式（３）で表される化合物は、単独でも２種以上を併用し混合しても用いることができる。
【００２６】
本発明による電子受容性化合物はそれぞれ１種または２種以上を混合して使用してもよく、通常無色ないし淡色の染料前駆体に対する本発明による電子受容性化合物の使用量は、５〜５０００重量％、好ましくは１０〜３０００重量％である。
【００２７】
本発明に用いられる通常無色ないし淡色の電子供与性染料前駆体としては一般に感圧記録紙や感熱記録紙等に用いられる公知な化合物に代表されるが、特に制限されるものではない。具体的な例としては、例えば下記に挙げるものなどがあるが、本発明はこれに限定されるものではない。
【００２８】
（１）トリアリールメタン系化合物
３，３−ビス（ｐ−ジメチルアミノフェニル）−６−ジメチルアミノフタリド（クリスタルバイオレットラクトン）、３，３−ビス（ｐ−ジメチルアミノフェニル）フタリド、３−（ｐ−ジメチルアミノフェニル）−３−（１，２−ジメチルインドール−３−イル）フタリド、３−（ｐ−ジメチルアミノフェニル）−３−（２−メチルインドール−３−イル）フタリド、３−（ｐ−ジメチルアミノフェニル）−３−（２−フェニルインドール−３−イル）フタリド、３−（４−ジエチルアミノ−２−エトキシフェニル）−３−（１−エチル−２−メチルインドール−３−イル）フタリド、３−（４−ジエチルアミノ−２−エトキシフェニル）−３−（１−エチル−２−メチルインドール−３−イル）−４−アザフタリド、３−（４−ジエチルアミノ−２−エトキシフェニル）−３−（１−エチル−２−メチルインドール−３−イル）−４，７−ジアザフタリド、３−（４−ジエチルアミノ−２−エトキシフェニル）−３−（１−エチル−２−メチルインドール−３−イル）−７−アザフタリド、３−（ｐ−ジメチルアミノフェニル）−３−（２−フェニルインドール−３−イル）フタリド、３，３−ビス（１，２−ジメチルインドール−３−イル）−５−ジメチルアミノフタリド、３，３−ビス（１，２−ジメチルインドール−３−イル）−６−ジメチルアミノフタリド、３，３−ビス（９−エチルカルバゾール−３−イル）−５−ジメチルアミノフタリド、３，３−ビス（２−フェニルインドール−３−イル）−５−ジメチルアミノフタリド、３−ｐ−ジメチルアミノフェニル−３−（１−メチルピロール−２−イル）−６−ジメチルアミノフタリド、３，３−ビス（ｐ−ジメチルアミノフェニル）−４−アザフタリド等。
【００２９】
（２）ジフェニルメタン系化合物
４，４′−ビス（ジメチルアミノフェニル）ベンズヒドリルベンジルエーテル、Ｎ−クロロフェニルロイコオーラミン、Ｎ−２，４，５−トリクロロフェニルロイコオーラミン等。
【００３０】
（３）キサンテン系化合物
ローダミンＢアニリノラクタム、ローダミンＢ−ｐ−クロロアニリノラクタム、３−ジエチルアミノ−７−ジベンジルアミノフルオラン、３−ジエチルアミノ−７−オクチルアミノフルオラン、３−ジエチルアミノ−７−フェニルフルオラン、３−ジエチルアミノ−７−フェノキシフルオラン、３−ジエチルアミノ−７−クロロフルオラン、３−ジエチルアミノ−６−クロロ−７−メチルフルオラン、３−ジエチルアミノ−７−（３，４−ジクロロアニリノ）フルオラン、３−ジエチルアミノ−７−（２−クロロアニリノ）フルオラン、
【００３１】
３−ジエチルアミノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−エチル−Ｎ−トリル）アミノ−６−メチル−７−アニリノフルオラン、３−ピペリジノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−エチル−Ｎ−トリル）アミノ−６−メチル−７−フェネチルフルオラン、３−ジエチルアミノ−７−（４−ニトロアニリノ）フルオラン、３−ジブチルアミノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−メチル−Ｎ−プロピル）アミノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−エチル−Ｎ−イソアミル）アミノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−メチル−Ｎ−シクロヘキシル）アミノ−６−メチル−７−アニリノフルオラン、３−（Ｎ−エチル−Ｎ−テトラヒドロフリル）アミノ−６−メチル−７−アニリノフルオラン等。
【００３２】
（４）チアジン系化合物
ベンゾイルロイコメチレンブルー、ｐ−ニトロベンゾイルロイコメチレンブルー等。
【００４４】
（５）スピロ系化合物
３−メチルスピロジナフトピラン、３−エチルスピロジナフトピラン、３，３′−ジクロロスピロジナフトピラン、３−ベンジルスピロジナフトピラン、３−メチルナフト−（３−メトキシベンゾ）スピロピラン、３−プロピルスピロベンゾピラン等。
【００３３】
前記通常無色ないし淡色の染料前駆体は単独でも、または２種以上を混合して使用してもよい。
【００３４】
本発明の可逆性感熱記録材料の製造方法の具体例としては、染料前駆体と可逆性顕色剤を主成分とし、これに本発明による化合物を添加し、支持体上に塗布して可逆性感熱記録層を形成する方法が挙げられる。
【００３５】
染料前駆体と可逆性顕色剤及び本発明による化合物を可逆性感熱記録層に含有させるための塗液作製方法としては、各々の化合物を単独で溶媒に溶解もしくは分散媒に分散してから混合する方法、各々の化合物を混ぜ合わせてから溶媒に溶解もしくは分散媒に分散する方法、各々の化合物を加熱溶解し均一化した後冷却し、溶媒に溶解もしくは分散媒に分散する方法等が挙げられるが、特に限定されるものではない。分散時には必要なら分散剤を用いてもよい。水を分散媒として使う場合の分散剤としてはポリビニルアルコール等の水溶性高分子や各種の界面活性剤が利用できる。水系の分散の際は、エタノール等の水溶性有機溶媒を混合してもよい。この他に炭化水素類に代表される有機溶媒が分散媒の場合は、レシチンや燐酸エステル類等を分散剤に用いてもよい。
【００３６】
また、可逆性感熱記録層の強度を向上する等の目的でバインダーを可逆性感熱記録層中に添加する事も可能である。バインダーの具体例としては、デンプン類、ヒドロキシエチルセルロース、メチルセルロース、カルボキシメチルセルロース、ゼラチン、カゼイン、ポリビニルアルコール、変性ポリビニルアルコール、ポリアクリル酸ソーダ、アクリル酸アミド／アクリル酸エステル共重合体、アクリル酸アミド／アクリル酸エステル／メタクリル酸３元共重合体、スチレン／無水マレイン酸共重合体のアルカリ塩、エチレン／無水マレイン酸共重合体のアルカリ塩等の水溶性高分子、ポリ酢酸ビニル、ポリウレタン、ポリアクリル酸エステル、スチレン／ブタジエン共重合体、アクリロニトリル／ブタジエン共重合体、アクリル酸メチル／ブタジエン共重合体、エチレン／酢酸ビニル共重合体、エチレン／塩化ビニル共重合体、ポリ塩化ビニル、エチレン／塩化ビニリデン共重合体、ポリ塩化ビニリデン等のラテックス類が挙げられる。これらのバインダーの役割は、組成物の各素材が印字、消去の熱印加によって片寄ることなく均一に分散した状態を保つことにある。したがって、バインダー樹脂には耐熱性の高い樹脂を用いることが好ましい。最近になって、プリペイドカード、ストアドカードといった付加価値の高い可逆性感熱記録材料が用いられることが多くなり、それに伴い、耐熱性、耐水性、さらには接着性といった高耐久品が要求されるようになってきている。このような要求に対しては、硬化性樹脂は特に好ましい。
【００３７】
硬化性樹脂としては、例えば熱硬化性樹脂、電子線硬化樹脂、紫外線硬化樹脂等が挙げられる。熱硬化性樹脂としては、例えばフェノキシ樹脂、ポリビニルブチラール樹脂、セルロースアセテートプロピオネート樹脂等の水酸基、カルボキシル基が架橋剤と反応し、硬化するものが挙げられる。この際の架橋剤としては、例えば、イソシアネート類、アミン類、フェノール類、エポキシ類等が挙げられる。
【００３８】
電子線および硬化線樹脂に用いられるモノマーとしては、アクリル系に代表される単官能性モノマー、二官能モノマー、多官能モノマー等が挙げられるが、特に紫外線架橋の際には光重合開始剤、光重合促進剤を用いる。
【００３９】
また、可逆性感熱記録層の発色感度を調節するための添加剤として、熱可融性物質を可逆性感熱記録層中に含有させることもできる。６０℃〜２００℃の融点を有するものが好ましく、特に８０℃〜１８０℃の融点を有するものが好ましい。一般の感熱記録紙に用いられている増感剤を使用することもできる。これらの化合物としては、Ｎ−ヒドロキシメチルステアリン酸アミド、ベヘン酸アミド、ステアリン酸アミド、パルミチン酸アミドなどのワックス類、２−ベンジルオキシナフタレン等のナフトール誘導体、ｐ−ベンジルビフェニル、４−アリルオキシビフェニル等のビフェニル誘導体、１，２−ビス（３−メチルフェノキシ）エタン、２，２′−ビス（４−メトキシフェノキシ）ジエチルエーテル、ビス（４−メトキシフェニル）エーテル等のポリエーテル化合物、炭酸ジフェニル、シュウ酸ジベンジル、シュウ酸ビス（ｐ−メチルベンジル）エステル等の炭酸またはシュウ酸ジエステル誘導体等があげられ、２種以上併用して添加することもできる。
【００４０】
本発明の可逆性感熱記録材料に用いられる支持体としては、紙、各種不織布、織布、ポリエチレンテレフタレートやポリプロピレン等の合成樹脂フィルム、ポリエチレン、ポリプロピレン等の合成樹脂をラミネートした紙、合成紙、金属箔、ガラス等、あるいはこれらを組み合わせた複合シートを目的に応じて任意に用いることができるが、これらに限定されるものではなく、これらは不透明、半透明或いは透明のいずれであってもよい。地肌を白色その他の特定の色に見せるために、白色顔料や有色染顔料や気泡を支持体中又は表面に含有させても良い。特にフィルム類等水性塗布を行なう場合で支持体の親水性が小さく可逆性感熱記録層の塗布困難な場合は、コロナ放電等による表面の親水化処理やバインダーに用いるのと同様の水溶性高分子類を、支持体表面に塗布するなどの易接着処理してもよい。
【００４１】
本発明の可逆性感熱記録材料の層構成は、可逆性感熱記録層のみであっても良い。必要に応じて、可逆性感熱記録層上に保護層を設けることも又、可逆性感熱記録層と支持体の間に水溶性高分子や白色ないし有色染顔料や中空粒子のいずれか一つ以上を含む中間層を設けることもできる。この場合、保護層および／または中間層は２層ないしは３層以上の複数の層から構成されていてもよい。可逆性感熱記録層も各成分を一層ずつに含有させたり層別に配合比率を変化させたりして２層以上の多層にしてもよい。更に、可逆性感熱記録層中および／または他の層および／または可逆性感熱記録層が設けられている面と反対側の面に、電気的、光学的、磁気的に情報が記録可能な材料を含んでも良い。また、可逆性感熱記録層が設けられている面と反対側の面にブロッキング防止、カール防止、帯電防止を目的としてバックコート層を設けることもできる。
【００４２】
なお、本発明における各層を支持体上に積層し、本発明の可逆性感熱記録材料を形成する方法は特に制限されるものではなく、従来の方法により形成することができる。例えば、エアーナイフコーター、ブレードコーター、バーコーター、カーテンコーター等の塗抹装置、平版、凸版、凹版、フレキソ、グラビア、スクリーン、ホットメルト等の方式による各種印刷機等を用いる事が出来る。さらに通常の乾燥工程の他、ＵＶ照射・ＥＢ照射により各層を保持させる事が出来る。
【００４３】
可逆性感熱記録層は、各成分を微粉砕して得られる各々の分散液を混合し、支持体上に塗布乾燥する方法、各成分を溶媒に溶解して得られる各々の溶液を混合し、支持体上に塗布乾燥する方法などにより得ることができる。乾燥条件は水等の分散媒ないし溶媒によっても異なる。この他に各成分を混合し加熱して可融分を溶融し熱時塗布する方法もある。
【００４４】
また、可逆性感熱記録層及び／または保護層及び／または中間層には、ケイソウ土、タルク、カオリン、焼成カオリン、炭酸カルシウム、炭酸マグネシウム、酸化チタン、酸化亜鉛、酸化ケイ素、水酸化アルミニウム、尿素−ホルマリン樹脂等の顔料、その他に、ヘッド摩耗防止、スティッキング防止等の目的でステアリン酸亜鉛、ステアリン酸カルシウム等の高級脂肪酸金属塩、パラフィン、酸化パラフィン、ポリエチレン、酸化ポリエチレン、ステアリン酸アミド、カスターワックス等のワックス類を、また、ジオクチルスルホコハク酸ナトリウム等の分散剤、さらに界面活性剤、蛍光染料、紫外線吸収剤などを含有させることもできる。
【００４５】
次に、本発明の可逆性感熱記録材料の発色及び消色方法について述べる。発色を行うには、加熱に引き続き急速な冷却が起これば良く、例えばサーマルヘッド、レーザー光等による加熱により可能である。又、加熱後ゆっくり冷却すれば消色し、例えばサーマルヘッド、熱ロール、熱スタンプ、高周波加熱、熱風、電熱ヒーター及びタングステンランプ、ハロゲンランプ等の光源などからの輻射熱等を用いることにより行うことができる。
【００４６】
【作用】
本発明の感熱記録材料の画像形成及び消去原理は未だ明確ではないが、以下の様に考えられる。通常無色ないし淡色の染料前駆体は、フェノール性化合物のような電子受容性化合物と共に加熱すると染料前駆体から電子受容性化合物への電子移動が起こり発色する。この時、電子受容性化合物分子は発色した染料分子の極めて近傍に存在していると考えられる。また、発色した染料分子から電子受容性化合物分子を引き離すと、発色した染料分子は再び電子を受け取り、発色前の染料前駆体の状態となる。本発明は加熱により、電子受容性化合物分子と染料分子との距離を変化させ発色及び消色を行うものと考えられる。
【００４７】
さらに詳しく述べるならば、これまでに可逆性顕色剤と呼ばれる電子受容性化合物の多くは、その構造の中に脂肪鎖を持つため、染料前駆体分子および発色した染料分子との相溶性が低く、凝固した状態では互いに殆ど溶け合わないと考えられる。また、加熱溶融状態の様に染料前駆体分子と可逆性顕色剤分子が自由に運動できる状態では、染料前駆体分子と可逆性顕色剤分子は互いにある割合で溶け合い、発色状態となる。それ故、発色している溶融状態の混合物をゆっくり冷却すると、降温するに従い可逆顕色剤分子と染料分子は互いに溶け合わなくなり相分離し、消色する。特に、本発明に好ましく使用される一般式化７〜８で表される電子受容性化合物は分子内に、アミド結合等の水素結合能力を持つ結合を含有しているため、分子間水素結合により速やかに結晶化してしまうと考えられる。一方、急速に冷却を行うと、相分離する前、即ち発色状態のままで固化するため、発色状態が固定され固化後も発色状態が安定に保持される。
【００４８】
本発明に於いて用いられる一般式（３）で表される消色促進化合物はアンモニウム塩であり、この様な化合物は融点以上に加熱した後、室温まで放冷した場合、再固化するのにある程度の時間を必要とするものが多い。即ちこの特性は、降温後の電子供与性染料前駆体と電子受容性可逆性顕色剤の相分離時に、消色時間ををより助長しているものと考えられ、その結果より低温度で消色可能となった。
【００４９】
【実施例】
以下実施例によって本発明を更に詳しく説明する。実施例中の部数や百分率は重量基準である。
【００５０】
実施例
（Ａ）可逆性感熱塗液の作製
３−（４−ジエチルアミノ−２−エトキシフェニル）−３−（１−エチル−２−メチルインドール−３−イル）−４−アザフタリド４０部とＮ−［３−（ｐ−ヒドロキシフェノキシ）プロピオノ］−Ｎ′−ｎ−オクタデカノヒドラジド１００部を８％ポリビニルアセタール（積水化学工業製、ＢＬ−１、アセタール化度６３モル％）のテトラヒドロフラン（ＴＨＦ）溶液９１００部と共にペイントコンディショナーで粉砕し可逆性顕色剤分散液（Ａ液）を得た。更に、Ｎ−オクタデシルスクシンイミド５部をＴＨＦ２０部と共にペイントコンディショナーで粉砕し消色促進剤分散液（Ｂ液）を得た。これらＡ、及びＢ液の２種の分散液を混合し、可逆性感熱塗液を作製した。
【００５１】
（Ｂ）可逆性感熱記録層の塗工
（Ａ）で作製した可逆性感熱塗液にコロネートＬ（日本ポリウレタン株式会社製）２９部を加えた後、ポリエチレンテレフタレート（ＰＥＴ）シートに、固形分塗抹量４．０ｇ／ｍ²となる様に塗抹した。６０℃で２４時間乾燥し、スーパ ーカレンダーで処理して可逆性感熱記録材料を得た。
【００５２】
（Ｃ）保護層の塗工
（Ｂ）で作製した塗工シート上に、アロニックスＭ８０３０（東亞合成化学工業製）９０部、Ｎ−ビニル−２−ピロリドン５部、イルガキュア５００（日本チバガイギー製）５部、及びニップシールＥ２２０Ａ（日本シリカ製）１０部を加え攪拌後、保護層の塗液とし、１．０ｇ／ｍ²となるように塗工した後、紫外線 照射装置にて硬化を行い、保護層を有する可逆性感熱記録材料を得た。
【００５３】
実施例に使用した電子供与性染料前駆体を化１１に示す。
【００５４】
【化１１】

【００５５】
実施例に使用した、本発明に好ましく用いられる一般式（１）〜（２）で表される電子受容性可逆性顕色剤、一般式（３）で表される消色促進化合物および電子供与性染料前駆体の組み合わせを表１に示す。
【００５６】
【表１】

【００５７】
比較例１
実施例２で用いた消色促進化合物を除いた他は、実施例２と同様にして可逆性感熱記録材料を得た。
【００５８】
比較例２
実施例５で用いた消色促進化合物の代わりに１，３−ジオクタデシル尿素を用いた他は、実施例５と同様にして可逆性感熱記録材料を得た。
【００５９】
試験１（発色濃度＝熱応答性）
実施例１〜６および比較例１〜２で得た可逆性感熱記録材料を、京セラ製印字ヘッドＫＪＴ−２５６−８ＭＧＦ１付き大倉電気製感熱ファクシミリ印字試験機ＴＨ−ＰＭＤを用いて印加パルス１.１ミリ秒で印加電圧２６ボルトの条件で 印字し、得られた発色画像の濃度を濃度計マクベスＲＤ９１８を用いて測定した。
【００６０】
試験２（画像の消去性）
実施例１〜６および比較例１〜２で得た可逆性感熱記録材料を、京セラ製印字ヘッドＫＪＴ−２５６−８ＭＧＦ１付き大倉電気製感熱ファクシミリ印字試験機ＴＨ−ＰＭＤを用いて印加パルス１.１ミリ秒で印加電圧２６ボルトの条件で 印字し、これを熱スタンプを用いて１２０℃で１秒間加熱した後、試験１と同様にして濃度を測定した。
【００６１】
試験３（消色開始温度）
実施例１〜６および比較例１〜２で得た可逆性感熱記録材料を、京セラ製印字ヘッドＫＪＴ−２５６−８ＭＧＦ１付き大倉電気製感熱ファクシミリ印字試験機ＴＨ−ＰＭＤを用いて印加パルス１.１ミリ秒で印加電圧２６ボルトの条件で 印字し、これを熱スタンプを用いて８０℃から１７０℃まで１０℃間隔で計１０箇所、各々１秒間加熱した後、試験１と同様にしてそれぞれの濃度を測定した。印字画像の光学濃度が０．１５を下回った加熱温度を消色開始温度とした。
【００６２】
試験４（発色濃度の経時変化＝画像安定性）
実施例１〜６および比較例１〜２で得た可逆性感熱記録材料を、京セラ製印字ヘッドＫＪＴ−２５６−８ＭＧＦ１付き大倉電気製感熱ファクシミリ印字試験機ＴＨ−ＰＭＤを用いて、印加パルス１.１ミリ秒で印加電圧２６ボルトの条件 で印字し、温度５０℃、相対湿度２０％の雰囲気下に２４時間保存した後、試験１と同様にして、発色部の濃度を測定し、下記数１により画像残存率を計算した。
【００６３】
【数１】

【００６４】
実施例１〜６および比較例１〜２の試験１〜４の結果を表２に示した。
【００６５】
【表２】

【００６６】
【発明の効果】
表２に示したように、通常無色ないし淡色の染料前駆体と、加熱により該染料前駆体に可逆的な色調変化を生じせしめる一般式（１）〜（２）で表される可逆性顕色剤とを含有する可逆性感熱記録材料において、一般式（３）で表される消色促進化合物を含有させる事により明瞭なコントラストで画像の形成・消去が可能で、日常生活の環境下で経時的に、安定な画像を保持可能な可逆性感熱記録材料を得ることができた。001
BACKGROUND OF THE INVENTION
  The present invention relates to a reversible thermosensitive recording material capable of forming and erasing images by controlling thermal energy.
[002]
[Prior art]
  In general, a heat-sensitive recording material is a material in which a heat-sensitive recording layer mainly comprising an electron-donating usually colorless or light-colored dye precursor and an electron-accepting developer is provided on a support. By heating with a pen, laser light or the like, the dye precursor and the developer react instantaneously to obtain a recorded image, which is disclosed in Japanese Patent Publication Nos. 43-4160 and 45-14039. ing.
003
  In general, such a heat-sensitive recording material cannot be erased and returned to the state before image formation once an image is formed. There was no choice but to add to. For this reason, when the area of the thermal recording portion is limited, the recordable information is limited, and all necessary information cannot be recorded.
[004]
  In recent years, a reversible thermosensitive recording material capable of repeatedly forming and erasing an image has been devised in order to cope with such a problem. For example, Japanese Patent Laid-Open Nos. 54-119377 and 63-39377 are proposed. JP-A-63-41186 describes a heat-sensitive recording material composed of a resin base material and small organic molecules dispersed in the resin base material. However, since this method reversibly changes the transparency of the heat-sensitive recording material by heat energy, the contrast between the image forming portion and the non-image forming portion is insufficient.
[005]
  In the methods described in JP-A-50-81157 and JP-A-50-105555, the image to be formed changes according to the environmental temperature, so that the image forming state and the erasing state are maintained. The temperatures are different, and these two states cannot be stably maintained for an arbitrary period at room temperature.
[006]
  Furthermore, Japanese Patent Application Laid-Open No. 59-120492 describes a method of maintaining the image forming state / erased state by using the hysteresis characteristic of the color component and maintaining the recording material in the hysteresis temperature range. In this method, a heating source and a cooling source are required for image formation and erasure, and the temperature range in which the image formation state and the erasure state can be maintained is limited to the hysteresis temperature range. It is still insufficient for use in
[007]
  On the other hand, in JP-A-2-188293, JP-A-2-188294, and International Publication No. WO90 / 11898, a reversible sensation composed of a leuco dye and a color-reducing agent that develops and decolors the leuco dye by heating. A thermal recording medium is described. The developer / subtractor is an amphoteric compound that has an acidic group that develops color of the leuco dye and a basic group that erases the developed leuco dye, and has a color developing action by the acidic group or a decoloring action by the basic group by controlling thermal energy. One is preferentially generated, and coloring and decoloring are performed. However, with this method, it is impossible to completely switch between the color developing reaction and the color erasing reaction only by controlling the heat energy, and since both reactions occur at a certain ratio simultaneously, a sufficient color density cannot be obtained, and the color erasing reaction cannot be obtained. Cannot be done completely. Therefore, sufficient image contrast cannot be obtained. Further, since the decoloring action of the basic group also acts on the color developing part at room temperature, the phenomenon that the density of the color developing part decreases with time is unavoidable. Further, JP-A-5-124360 describes a reversible thermosensitive recording medium that develops and decolors a leuco dye by heating. As an electron accepting compound, an organic phosphonic acid compound, an α-hydroxy aliphatic carboxylic acid, Specific phenol compounds such as fatty acid dicarboxylic acids and alkylthiophenols having 12 or more aliphatic groups, alkyloxyphenols, alkylcarbamoylphenols, gallic acid alkyl esters are exemplified. However, even this recording medium cannot solve the two problems of low color density or incomplete erasing at the same time, and it is satisfactory in terms of stability over time of the image. Absent. Further, in JP-A-5-294063, fatty acid, wax, higher alcohol, phosphoric acid / benzoic acid / phthalic acid or oxyacid is used as a decoloring accelerator for improving the erasability of the reversible thermosensitive recording medium. Various esters, silicone oils, liquid crystal compounds, surfactants and fatty acid saturated hydrocarbons having 10 or more carbon atoms have been disclosed, but since their effects are small, the image density at the time of erasing is still high and practical. I can't say that.
[008]
  As described above, the conventional technology has a clear image contrast, enables the formation and complete erasure of high-density images, and is a practical reversible thermosensitive recording capable of maintaining a stable image over time in the environment of daily life. The production of the material has been difficult. On the other hand, in Japanese Patent Application No. 10-93313, the present applicants have proposed an electron that causes reversible color change, that is, color development and decoloration, by heating a normally colorless or light-colored electron-donating dye precursor. Although it has been found that a receptive compound (reversible developer) exists, in order to obtain a practically better image quality and an easy-to-use recording medium, the image density at the time of decoloring, the decoloring start temperature and There was room for improvement in the decoloring temperature range.
[0109]
[Problems to be solved by the invention]
  An object of the present invention is to provide a heat-sensitive recording material capable of forming and erasing an image with a good contrast and capable of holding a stable image over time in an environment of daily life. More specifically, the present invention provides a reversible thermosensitive recording material that has a lower image density at the time of color erasure, less unerased, and can be erased uniformly at a lower temperature and in a wide temperature range. This is the issue.
[0010]
[Means for Solving the Problems]
  The inventors of the present invention generally contain a colorless or light dye precursor on a support and a reversible developer that causes a reversible color change in the dye precursor due to a difference in cooling rate after heating. In the reversible thermosensitive recording material, the reversible developer is as follows:When using at least one of the compounds represented by the general formulas (1) and (2),As a result of intensive studies to further improve its erasability,General formula (3)By adding at least one of the specific compounds represented by the above, it was found that a reversible thermosensitive recording material capable of completely and uniformly erasing images in a wide temperature range was obtained, and the present invention was completed. It came.
[0011]
[Formula 4]

  (In formula 1, q represents an integer of 1 or more and 3 or less.R ^Three Represents a divalent aliphatic hydrocarbon group having 1 to 11 carbon atoms. R ^Four Represents an aliphatic hydrocarbon group having 6 to 11 carbon atoms which may contain an oxygen atom or a sulfur atom in the chain. Z is diacyl hydrazide (-CONHNHCO-), oxalic acid diamide (-NHCOCONH-), acylurea (-CONHCONH-, -NHCONHCO-), 3-acylcarbazic acid ester (-CONHNHCOO-), semicarbazide (-NHCONHNH-, -NHNHCONH-), acyl semicarbazide (-CONHNHCONH-, -NHCONHNHCO-), diacylaminomethane (-CONHCH) ₂ NHCO-), 1-acylamino-1-ureidomethane (-CONHCH ₂ NHCONH-, -NHCONHCH ₂ NHCO-), malonamide (-NHCOCH ₂ Represents one of divalent linking groups selected from CONH-). )
[0012]
[Chemical formula 5]

  (In Formula 2, r represents an integer of 1 or more and 3 or less. R^FiveIs carbon number2 to 11The divalent hydrocarbon group of R⁶Represents a hydrocarbon group having 1 to 24 carbon atoms which may contain an oxygen atom or a sulfur atom in the chain. Q and T are synonymous and may be the same or different from each other.Amides (-CONH-, -NHCO-), ureas (-NHCONH-), urethanes (-NHCOO-, -OCONH-), diacylhydrazides (-CONHNHCO-), oxalic acid diamides (-NHCONCONH-), acylureas (- CONHCONH-, -NHCONHCO-), 3-acylcarbazic acid ester (-CONHNHCOO-), semicarbazide (-NHCONHNH-, -NHNHCONH-), acyl semicarbazide (-CONHNHCONH-, -NHCONHNHCO-), diacylaminomethane (-CONHCH ₂ NHCO-), 1-acylamino-1-ureidomethane (-CONHCH ₂ NHCONH-, -NHCONHCH ₂ NHCO-), malonamide (-NHCOCH ₂ One of divalent groups selected from CONH-). )
[0013]
[Chemical 6]

  (In Formula 3, R⁷, R⁸And R⁹Is synonymous and represents an alkyl group, an aralkyl group, an alkenyl group and an aryl group which may be the same or different from each other, and these may have a substituent or may form a ring with each other Good. R^TenRepresents a hydrocarbon group having 6 to 24 carbon atoms. t represents 1 or 2; A represents an anion, and w represents a number necessary for adjusting the charge in the molecule to zero. )
[0014]
  Used in the present invention,General formula (1)-(2)The reversible developer represented by the above formulas is disclosed in JP-A-7-108761, JP-A-7-179043, JP-A-7-164746, and Japanese Patent Application No. 11-69787. And Japanese Patent Application No. 10-315252, etc., and the synthesis method is also described.
[0015]
In the compound represented by the general formula (1), R ^Three Represents a divalent aliphatic hydrocarbon group having 1 to 11 carbon atoms. R ^Four Represents an aliphatic hydrocarbon group having 6 to 11 carbon atoms which may contain an oxygen atom or a sulfur atom in the chain. Z is diacyl hydrazide (-CONHNHCO-), oxalic acid diamide (-NHCOCONH-), acylurea (-CONHCONH-, -NHCONHCO-), 3-acylcarbazic acid ester (-CONHNHCOO-), semicarbazide (-NHCONHNH-, -NHNHCONH-), acyl semicarbazide (-CONHNHCONH-, -NHCONHNHCO-), diacylaminomethane (-CONHCH) ₂ NHCO-), 1-acylamino-1-ureidomethane (-CONHCH ₂ NHCONH-, -NHCONHCH ₂ NHCO-), malonamide (-NHCOCH ₂ Represents one of divalent linking groups selected from CONH-). ) In general formula (1), benzene ring and R ^Three The linking group is an oxygen atom, but generally has good erasability, so R ^Three , R ^Four The linking group having an amide bond represented by X as the minimum structural unit is shorter, and the smaller the hydrogen bonding ability, the better the color development and the better the color-decoloration balance. is there.
[0016]
  less than,General formula (1)Specific examples of electron-accepting compounds represented by7However, the present invention is not limited to this.
[0017]
[Chemical 7]

[0018]
  In the compound represented by the general formula (2), R ^Five Is a divalent hydrocarbon group having 2 to 11 carbon atoms, R ⁶ Represents a hydrocarbon group having 1 to 24 carbon atoms which may contain an oxygen atom or a sulfur atom in the chain. Q and T are synonymous and may be the same or different from each other. Amide (—CONH—, —NHCO—), Urea (—NHCONH—), Urethane (—NHCOO—, —OCONH—), Diacyl Hydrazide (-CONHNHCO-), oxalic acid diamide (-NHCONCONH-), acylurea (-CONHCONH-, -NHCONHCO-), 3-acylcarbazic acid ester (-CONHNHCOO-), semicarbazide (-NHCONHNH-, -NHNHCONH- ), Acyl semicarbazide (—CONHNHCONH—, —NHCONHNHCO—), diacylaminomethane (—CONHCH) ₂ NH CO-), 1-acylamino-1-ureidomethane (-CONHCH ₂ NHCONH-, -NHCONHCH ₂ NHCO-), malonamide (-NHCOCH ₂ One of divalent groups selected from CONH-).
[0019]
  less than,General formula (2)Specific examples of electron-accepting compounds represented by8However, the present invention is not limited to this.
[0020]
[Chemical 8]

[0021]
  General formula (3)In the compound represented by R⁷, R⁸And R⁹Represents the same or different alkyl group, aralkyl group, alkenyl group and aryl group, preferably a lower alkyl group having 6 or less carbon atoms. Furthermore, these may be connected to each other to form an alicyclic structure, but at this time, a hetero atom such as an oxygen atom or a nitrogen atom may be contained in the chain. R^TenRepresents a monovalent or divalent hydrocarbon group having 6 to 24 carbon atoms, preferably an aliphatic hydrocarbon group, and specifically monovalent having 8 to 18 carbon atoms. A represents a counter anion, and specific examples thereof include halogen, substituted sulfonate, substituted borate, substituted phosphate and the like, preferably halogen and substituted sulfonate.
[0022]
  General formula (3)Specific examples of the compound represented byChemical formula 9and10Although the compound shown to these is mentioned, this invention is not limited to this.
[0023]
[Chemical 9]

[0024]
Embedded image

[0025]
  General formula (3)The preferred amount of the compound represented byGeneral formula (1)-(2)It is 0.1 to 1000 weight% with respect to the electron-accepting compound represented by these, More preferably, it is 0.5 to 200 weight%. Further, considering the heat-resistant storage stability of the printed image, the content is most preferably 1% by weight or more and 100% by weight or less. Also,General formula (3)The compounds represented by can be used singly or in combination of two or more.
[0026]
  The electron-accepting compound according to the present invention may be used alone or in combination of two or more kinds. The amount of the electron-accepting compound according to the present invention is usually 5 to 5000 weights with respect to a colorless or light dye precursor. %, Preferably 10 to 3000% by weight.
[0027]
  The usually colorless or light-colored electron-donating dye precursor used in the present invention is typically represented by known compounds used for pressure-sensitive recording paper, heat-sensitive recording paper, etc., but is not particularly limited. Specific examples include the following, but the present invention is not limited thereto.
[0028]
(1) Triarylmethane compounds
  3,3-bis (p-dimethylaminophenyl) -6-dimethylaminophthalide (crystal violet lactone), 3,3-bis (p-dimethylaminophenyl) phthalide, 3- (p-dimethylaminophenyl) -3 -(1,2-dimethylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3- (2-methylindol-3-yl) phthalide, 3- (p-dimethylaminophenyl) -3 -(2-phenylindol-3-yl) phthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) phthalide, 3- (4-diethylamino) -2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide, 3- (4-diethyl) Mino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4,7-diazaphthalide, 3- (4-diethylamino-2-ethoxyphenyl) -3- (1-ethyl) -2-methylindol-3-yl) -7-azaphthalide, 3- (p-dimethylaminophenyl) -3- (2-phenylindol-3-yl) phthalide, 3,3-bis (1,2-dimethyl) Indol-3-yl) -5-dimethylaminophthalide, 3,3-bis (1,2-dimethylindol-3-yl) -6-dimethylaminophthalide, 3,3-bis (9-ethylcarbazole) 3-yl) -5-dimethylaminophthalide, 3,3-bis (2-phenylindol-3-yl) -5-dimethylaminophthalide, 3-p-dimethylaminophenyl- - (1-methyl-pyrrol-2-yl) -6-dimethylaminophthalide, 3,3-bis (p- dimethylaminophenyl) -4-azaphthalide, and the like.
[0029]
(2) Diphenylmethane compounds
  4,4'-bis (dimethylaminophenyl) benzhydrylbenzyl ether, N-chlorophenylleucooramine, N-2,4,5-trichlorophenylleucooramine and the like.
[0030]
(3) Xanthene compounds
  Rhodamine B anilinolactam, rhodamine Bp-chloroanilinolactam, 3-diethylamino-7-dibenzylaminofluorane, 3-diethylamino-7-octylaminofluorane, 3-diethylamino-7-phenylfluorane, 3 -Diethylamino-7-phenoxyfluorane, 3-diethylamino-7-chlorofluorane, 3-diethylamino-6-chloro-7-methylfluorane, 3-diethylamino-7- (3,4-dichloroanilino) fluorane, 3-diethylamino-7- (2-chloroanilino) fluorane,
[0031]
  3-diethylamino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-anilinofluorane, 3-piperidino-6-methyl-7-ani Linofluorane, 3- (N-ethyl-N-tolyl) amino-6-methyl-7-phenethylfluorane, 3-diethylamino-7- (4-nitroanilino) fluorane, 3-dibutylamino-6-methyl-7 -Anilinofluorane, 3- (N-methyl-N-propyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-isoamyl) amino-6-methyl-7-ani Linofluorane, 3- (N-methyl-N-cyclohexyl) amino-6-methyl-7-anilinofluorane, 3- (N-ethyl-N-tetrahydrofuryl) amino-6-methyl 7-anilinofluoran like.
[0032]
(4) Thiazine compounds
  Benzoyl leucomethylene blue, p-nitrobenzoyl leucomethylene blue, etc.
[0044]
(5) Spiro compounds
  3-methylspirodinaphthopyran, 3-ethylspirodinaphthopyran, 3,3'-dichlorospirodinaphthopyran, 3-benzylspirodinaphthopyran, 3-methylnaphtho (3-methoxybenzo) spiropyran, 3-propyl Spirobenzopyran etc.
[0033]
  The usually colorless to light color dye precursors may be used alone or in admixture of two or more.
[0034]
  Specific examples of the method for producing the reversible thermosensitive recording material of the present invention include a dye precursor and a reversible developer as main components, and the compound according to the present invention is added thereto and coated on a support to reversible feel. The method of forming a thermal recording layer is mentioned.
[0035]
  The coating liquid preparation method for incorporating the dye precursor, the reversible developer, and the compound according to the present invention into the reversible thermosensitive recording layer includes dissolving each compound alone in a solvent or dispersing in a dispersion medium and mixing. A method in which each compound is mixed and then dissolved in a solvent or dispersed in a dispersion medium, a method in which each compound is dissolved by heating, homogenized, cooled, and dissolved in a solvent or dispersed in a dispersion medium. However, it is not particularly limited. If necessary, a dispersing agent may be used during dispersion. As a dispersant when water is used as a dispersion medium, water-soluble polymers such as polyvinyl alcohol and various surfactants can be used. In aqueous dispersion, a water-soluble organic solvent such as ethanol may be mixed. In addition, when an organic solvent typified by hydrocarbons is a dispersion medium, lecithin, phosphate esters, or the like may be used as a dispersant.
[0036]
  In addition, a binder can be added to the reversible thermosensitive recording layer for the purpose of improving the strength of the reversible thermosensitive recording layer. Specific examples of the binder include starches, hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, gelatin, casein, polyvinyl alcohol, modified polyvinyl alcohol, sodium polyacrylate, acrylic acid amide / acrylic acid ester copolymer, acrylic acid amide / acrylic. Water-soluble polymers such as acid ester / methacrylic acid terpolymer, alkali salt of styrene / maleic anhydride copolymer, alkali salt of ethylene / maleic anhydride copolymer, polyvinyl acetate, polyurethane, polyacrylic acid Esters, styrene / butadiene copolymers, acrylonitrile / butadiene copolymers, methyl acrylate / butadiene copolymers, ethylene / vinyl acetate copolymers, ethylene / vinyl chloride copolymers, polyvinyl chloride, ethylene Vinylidene chloride copolymers, latexes such as polyvinylidene chloride. The role of these binders is to keep the materials of the composition uniformly dispersed without being displaced by the application of heat for printing and erasing. Therefore, it is preferable to use a resin having high heat resistance as the binder resin. Recently, high value-added reversible thermosensitive recording materials such as prepaid cards and stored cards are often used, and accordingly, high durability products such as heat resistance, water resistance, and adhesiveness are required. It is becoming. For such a requirement, a curable resin is particularly preferable.
[0037]
  Examples of the curable resin include a thermosetting resin, an electron beam curable resin, and an ultraviolet curable resin. Examples of the thermosetting resin include those that are cured by reacting a hydroxyl group or a carboxyl group with a crosslinking agent, such as phenoxy resin, polyvinyl butyral resin, and cellulose acetate propionate resin. Examples of the crosslinking agent at this time include isocyanates, amines, phenols, epoxies, and the like.
[0038]
  Monomers used for electron beams and cured wire resins include monofunctional monomers, bifunctional monomers, polyfunctional monomers, and the like typified by acrylics. A polymerization accelerator is used.
[0039]
  Further, as an additive for adjusting the color development sensitivity of the reversible thermosensitive recording layer, a thermofusible substance can be contained in the reversible thermosensitive recording layer. Those having a melting point of 60 ° C. to 200 ° C. are preferred, and those having a melting point of 80 ° C. to 180 ° C. are particularly preferred. Sensitizers used for general heat-sensitive recording paper can also be used. These compounds include N-hydroxymethyl stearamide, behenamide, stearamide, palmitic amide wax, naphthol derivatives such as 2-benzyloxynaphthalene, p-benzylbiphenyl, 4-allyloxybiphenyl. Biphenyl derivatives such as 1,2-bis (3-methylphenoxy) ethane, 2,2′-bis (4-methoxyphenoxy) diethyl ether, bis (4-methoxyphenyl) ether and other polyether compounds, diphenyl carbonate, Examples thereof include carbonic acid or oxalic acid diester derivatives such as dibenzyl oxalate and bis (p-methylbenzyl) oxalate, which can be added in combination of two or more.
[0040]
  Supports used in the reversible thermosensitive recording material of the present invention include paper, various nonwoven fabrics, woven fabrics, synthetic resin films such as polyethylene terephthalate and polypropylene, paper laminated with synthetic resins such as polyethylene and polypropylene, synthetic paper, metal Foil, glass, etc., or a composite sheet combining these can be arbitrarily used depending on the purpose, but is not limited to these, and these may be opaque, translucent or transparent. In order to make the background appear white or other specific colors, a white pigment, a colored dye pigment, or air bubbles may be included in the support or on the surface. In particular, when water-based coatings such as films are used and the hydrophilicity of the support is small and it is difficult to coat the reversible thermosensitive recording layer, the same water-soluble polymer as used for the surface hydrophilization treatment by corona discharge or the like or the binder is used. An adhesive may be applied to the surface of the support to facilitate adhesion.
[0041]
  The layer structure of the reversible thermosensitive recording material of the present invention may be only the reversible thermosensitive recording layer. If necessary, a protective layer may be provided on the reversible thermosensitive recording layer, and any one or more of a water-soluble polymer, white or colored dye pigment, and hollow particles may be provided between the reversible thermosensitive recording layer and the support. An intermediate layer containing can also be provided. In this case, the protective layer and / or the intermediate layer may be composed of a plurality of layers of two layers or three or more layers. The reversible thermosensitive recording layer may also be composed of two or more layers by adding each component one by one or changing the blending ratio for each layer. Further, a material capable of recording information electrically, optically, and magnetically in the reversible thermosensitive recording layer and / or on the surface opposite to the other layer and / or the surface on which the reversible thermosensitive recording layer is provided. May be included. In addition, a back coat layer can be provided on the surface opposite to the surface on which the reversible thermosensitive recording layer is provided for the purpose of preventing blocking, curling and antistatic.
[0042]
  The method for laminating each layer in the present invention on a support and forming the reversible thermosensitive recording material of the present invention is not particularly limited, and can be formed by a conventional method. For example, smearing devices such as an air knife coater, blade coater, bar coater, curtain coater, etc., and various printing machines such as lithographic plates, relief plates, intaglio plates, flexo, gravure, screen, hot melt, etc. can be used. Furthermore, each layer can be held by UV irradiation and EB irradiation in addition to a normal drying process.
[0043]
  The reversible thermosensitive recording layer is a method of mixing each dispersion obtained by finely pulverizing each component, coating and drying on a support, mixing each solution obtained by dissolving each component in a solvent, It can be obtained by a method of coating and drying on a support. Drying conditions vary depending on the dispersion medium or solvent such as water. In addition, there is a method in which each component is mixed and heated to melt the fusible component and applied while hot.
[0044]
  The reversible thermosensitive recording layer and / or protective layer and / or intermediate layer includes diatomaceous earth, talc, kaolin, calcined kaolin, calcium carbonate, magnesium carbonate, titanium oxide, zinc oxide, silicon oxide, aluminum hydroxide, urea. -Pigments such as formalin resin, other than fatty acid metal salts such as zinc stearate and calcium stearate, paraffin, oxidized paraffin, polyethylene, polyethylene oxide, stearamide, caster wax, etc. for the purpose of preventing head wear and sticking These waxes can also contain a dispersing agent such as sodium dioctyl sulfosuccinate, a surfactant, a fluorescent dye, an ultraviolet absorber and the like.
[0045]
  Next, the coloring and decoloring methods of the reversible thermosensitive recording material of the present invention will be described. In order to perform color development, it is sufficient that rapid cooling occurs following heating, and for example, heating by a thermal head, laser light, or the like is possible. Moreover, if it cools slowly after heating, it will decolorize, for example, using a thermal head, a heat roll, a heat stamp, high-frequency heating, hot air, an electric heater, and radiant heat from a light source such as a tungsten lamp and a halogen lamp. it can.
[0046]
[Action]
  The image forming and erasing principles of the heat-sensitive recording material of the present invention are not yet clear, but are considered as follows. Normally, when a colorless or light dye precursor is heated together with an electron-accepting compound such as a phenolic compound, electron transfer from the dye precursor to the electron-accepting compound occurs and color develops. At this time, it is considered that the electron-accepting compound molecule exists in the very vicinity of the colored dye molecule. When the electron-accepting compound molecule is separated from the colored dye molecule, the colored dye molecule receives electrons again and becomes a dye precursor state before coloring. In the present invention, it is considered that the distance between the electron-accepting compound molecule and the dye molecule is changed by heating to perform coloring and decoloring.
[0047]
  In more detail, since many of the electron accepting compounds so far called reversible developers have fatty chains in their structures, they have low compatibility with dye precursor molecules and colored dye molecules. In the solidified state, it is considered that they hardly melt together. In addition, in a state where the dye precursor molecule and the reversible developer molecule can freely move as in the heat-melted state, the dye precursor molecule and the reversible developer molecule are melted at a certain ratio to form a color state. Therefore, when the colored mixture that has been colored is cooled slowly, the reversible developer molecule and the dye molecule become insoluble and phase-separate and decolorize as the temperature decreases. In particular, preferably used in the present inventionGeneral formula 7-8Since the electron-accepting compound represented by the formula contains a bond having a hydrogen bonding ability such as an amide bond in the molecule, it is considered that the electron accepting compound is rapidly crystallized by intermolecular hydrogen bonding. On the other hand, when rapidly cooled, it solidifies before phase separation, that is, in a colored state, so that the colored state is fixed and the colored state is stably maintained even after solidification.
[0048]
  Used in the present inventionGeneral formula (3)The decolorization promoting compound represented by the formula is an ammonium salt, and such a compound often requires a certain amount of time for re-solidification when heated to the melting point or higher and then allowed to cool to room temperature. In other words, this characteristic is considered to further promote the decoloring time during the phase separation of the electron-donating dye precursor and the electron-accepting reversible developer after the temperature decrease. Color became possible.
[0049]
【Example】
  Hereinafter, the present invention will be described in more detail with reference to examples. The parts and percentages in the examples are based on weight.
[0050]
  Example
(A) Preparation of reversible thermosensitive coating liquid
  3- (4-Diethylamino-2-ethoxyphenyl) -3- (1-ethyl-2-methylindol-3-yl) -4-azaphthalide and N- [3- (p-hydroxyphenoxy) propiono]- 100 parts of N′-n-octadecanohydrazide was pulverized with a paint conditioner together with 9100 parts of a tetrahydrofuran (THF) solution of 8% polyvinyl acetal (manufactured by Sekisui Chemical Co., Ltd., BL-1, degree of acetalization 63 mol%). A colorant dispersion (liquid A) was obtained. Furthermore, 5 parts of N-octadecyl succinimide and 20 parts of THF were pulverized with a paint conditioner to obtain a decolorization accelerator dispersion (liquid B). These two types of dispersion liquids A and B were mixed to prepare a reversible thermosensitive coating liquid.
[0051]
(B) Reversible thermosensitive recording layer coating
  After adding 29 parts of Coronate L (manufactured by Nippon Polyurethane Co., Ltd.) to the reversible thermosensitive coating liquid prepared in (A), the solid content smear amount is 4.0 g / m on a polyethylene terephthalate (PET) sheet.²It was smeared to become. It was dried at 60 ° C. for 24 hours and treated with a super calender to obtain a reversible thermosensitive recording material.
[0052]
(C) Coating of protective layer
  On the coating sheet prepared in (B), 90 parts of Aronix M8030 (manufactured by Toagosei Co., Ltd.), 5 parts of N-vinyl-2-pyrrolidone, 5 parts of Irgacure 500 (manufactured by Ciba Geigy Japan), and nip seal E220A (Nippon Silica) (Product made) After adding 10 parts and stirring, it was set as the coating liquid of a protective layer, and 1.0 g / m²Then, curing was performed with an ultraviolet irradiation device to obtain a reversible thermosensitive recording material having a protective layer.
[0053]
  The electron donating dye precursor used in the examples11Shown in
[0054]
Embedded image

[0055]
  Used in the examples, preferably used in the present inventionGeneral formula (1)-(2)An electron-accepting reversible developer represented byGeneral formula (3)Table 1 shows combinations of the decolorization promoting compound and the electron donating dye precursor represented by formula (1).
[0056]
[Table 1]

[0057]
  Comparative Example 1
  Example 2Except for the decolorization promoting compound used inExample 2In the same manner, a reversible thermosensitive recording material was obtained.
[0058]
  Comparative Example 2
  Example 5Other than using 1,3-dioctadecylurea instead of the decolorization promoting compound used inExample 5In the same manner, a reversible thermosensitive recording material was obtained.
[0059]
  Test 1 (color density = thermal response)
  Examples 1-6 and Comparative Examples 1-2The reversible thermosensitive recording material obtained in step 1 was printed using an Okura Electric thermal facsimile printing tester TH-PMD with a Kyocera print head KJT-256-8MGF1 under an applied pulse of 1.1 milliseconds and an applied voltage of 26 volts. Then, the density of the obtained color image was measured using a densitometer Macbeth RD918.
[0060]
  Test 2 (image erasability)
  Examples 1-6 and Comparative Examples 1-2The reversible thermosensitive recording material obtained in step 1 was printed using an Okura Electric thermal facsimile printing tester TH-PMD with a Kyocera print head KJT-256-8MGF1 under an applied pulse of 1.1 milliseconds and an applied voltage of 26 volts. Then, this was heated at 120 ° C. for 1 second using a heat stamp, and the concentration was measured in the same manner as in Test 1.
[0061]
  Test 3 (decoloration start temperature)
  Examples 1-6 and Comparative Examples 1-2The reversible thermosensitive recording material obtained in step 1 was printed using an Okura Electric thermal facsimile printing tester TH-PMD with a Kyocera print head KJT-256-8MGF1 under an applied pulse of 1.1 milliseconds and an applied voltage of 26 volts. Then, this was heated at a 10 ° C. interval from 80 ° C. to 170 ° C. at a total of 10 locations for 1 second each, and each concentration was measured in the same manner as in Test 1. The heating temperature at which the optical density of the printed image fell below 0.15 was defined as the decoloring start temperature.
[0062]
  Test 4 (Change in color density over time = image stability)
  Examples 1-6 and Comparative Examples 1-2The reversible thermosensitive recording material obtained in 1) was applied using an Okura Electric thermal facsimile printing tester TH-PMD with a Kyocera print head KJT-256-8MGF1 under an applied pulse of 1.1 milliseconds and an applied voltage of 26 volts. After printing and storing in an atmosphere at a temperature of 50 ° C. and a relative humidity of 20% for 24 hours, the density of the color development portion was measured in the same manner as in Test 1, and the image residual ratio was calculated by the following equation (1).
[0063]
[Expression 1]

[0064]
  Examples 1-6 and Comparative Examples 1-2The results of Tests 1 to 4 are shown in Table 2.
[0065]
[Table 2]

[0066]
【The invention's effect】
  As shown in Table 2, usually a colorless or light-colored dye precursor and reversible color change is caused to the dye precursor by heating.General formula (1)-(2)In a reversible thermosensitive recording material containing a reversible developer represented byGeneral formula (3)A reversible thermosensitive recording material capable of forming and erasing an image with clear contrast and maintaining a stable image over time in an environment of daily life is obtained by including the decoloration promoting compound represented by I was able to.

Claims (1)

In a reversible thermosensitive recording material comprising a normally colorless or light-colored dye precursor on a support and a reversible developer that causes a reversible color change in the dye precursor due to a difference in cooling rate after heating. In addition, at least one compound represented by the following general formulas (1) and (2) is used as the reversible developer , and at least one compound represented by the following general formula (3) is used as a decoloring accelerator. A reversible thermosensitive recording material comprising

(In Formula 1, q represents an integer of 1 or more and 3 or less. R ³ represents a divalent aliphatic hydrocarbon group having 1 to 11 carbon atoms . R ⁴ may contain an oxygen atom or a sulfur atom in the chain. Represents a good aliphatic hydrocarbon group having 6 to 11 carbon atoms, Z is diacyl hydrazide (-CONHNHCO-), oxalic acid diamide (-NHCOCONH-), acylurea (-CONHCONH-, -NHCONHCO-), 3-acylcarba Diacid ester (—CONHNHCOO—), semicarbazide (—NHCONHNH—, —NHNHCONH—), acyl semicarbazide (—CONHNHCONH—, —NHCONHNHCO—), diacylaminomethane (—CONHCH ₂ NHCO— ), 1-acylamino-1-ureido methane (-CONHCH ₂ NHCONH -, - NHCONH H ₂ NHCO-), represents one of the divalent linking group selected from malonamide (-NHCOCH ₂ CONH-).)

(In Formula 2, r represents an integer of 1 to 3, R ⁵ represents a divalent hydrocarbon group having 2 to 11 carbon atoms, and R ⁶ may contain an oxygen atom or a sulfur atom in the chain. Represents a hydrocarbon group having 1 to 24 carbon atoms, Q and T are synonymous and may be the same as or different from each other, amide (—CONH—, —NHCO—), urea (—NHCONH—), Urethane (—NHCOO—, —OCONH—), diacyl hydrazide (—CONHNHCO—), oxalic acid diamide (—NHCOCONH—), acylurea (—CONHCONH—, —NHCONHCO—), 3-acylcarbazic acid ester (—CONHNHCOO) -), Semicarbazide (-NHCONHNH-, -NHNHCONH-), acyl semicarbazide (-CONHNHCONH-, -NHCO) NHNHCO-), diacyl aminomethane (-CONHCH ₂ NHCO -), 1- acylamino-1- Ureidometan _{(-CONHCH 2 NHCONH -, - NHCONHCH} 2 NHCO-), divalent selected from malonamide (-NHCOCH ₂ CONH-) Represents any of the groups

(In Formula 3, R ⁷ , R ⁸ , and R ⁹ are synonymous and represent an alkyl group, an aralkyl group, an alkenyl group, and an aryl group, which may be the same as or different from each other. R ¹⁰ represents a hydrocarbon group having 6 to 24 carbon atoms, t represents 1 or 2, A represents an anion, and w represents an intramolecular number. Represents the number required to adjust the charge to zero.)